The primary objective of this study is to determine the relative pharmacodynamic effect of various dose levels of metformin hydrochloride compared to placebo on fasting plasma glucose (FPG) in patients with NIDDM. The specific objectives are 1) to assess the time-course of effects on FPG for any particular dose level; 2) determine the minimum effective dose among the five study doses; and 3) to assess the effect of dose level and FPG level at baseline on response.